The present invention relates to a hybrid communication terminal which is connected to a computer, and more particularly to a hybrid communication terminal which receives the supply of power from the computer and can perform the handover while continuing the communication.
As a mobile communication system, there has been known a broadband mobile service which is based on an existing mobile network such as a High Speed Packet Access (HSPA) and 1xEVDO which are regarded as technology of 3G, particularly 3.5G of recent years. Further, an environment has been created where a user can make use of various networks which includes novel broadband mobile services such as WiMAX which is regarded as the next generation technology which realizes the wider broadband communication and LTE which will soon commercially available.
For this end, user contents are no longer limited to voice communication services, a mobile body dedicated internet with small capacity for mobile and an exchange of e-mails. That is, WiMAX and LTE allow users to sufficiently make use of broadband contents represented by motion picture streaming even under a mobile environment even when the lowering of a communication speed generated by a Doppler effect which occurs when the moving body moves at a high speed is taken into consideration. Further, with the advent of a low latency network represented by LTE, an environment where a VOIP service becomes fully available at a portable terminal has been created.
WiMAX and LTE which are novel broadband mobile services are excellent in high speed property compared to the 3G network which uses an existing mobile body network as a base. On the other hand, WiMAX and LTE are provided in a spotted manner with respect to service areas in an initial stage of practice. As a result, there is not yet provided a situation where WiMAX or LTE can be used in a single form anywhere and any place. Accordingly, a need has been increasing for a terminal which can automatically switch a communication mode in such a manner that the communication using WiMAX or LTE is conducted in an environment where WiMAX or LTE is available, and an existing 3G network having a wide service area is conducted in an area outside ranges of these high speed networks.
Further, in the connection switching between the 3G network and WiMAX/LTE, the maintenance of the continuity of communication is an important requisite in terms of providing services not only at the time of using VOIP but also at the time of using contents where data are continuously exchanged such as streaming service. Assuming a case where the connection switching between the existing network and WiMAX/LTE is possible in a situation where the continuity of communication is not maintained, the contents which a user can use are limited eventually. This becomes an obstacle for a communication provider and an Application Service Provider (ASP) who provide various and versatile services and hence, there has been a strong demand for the maintenance of the continuity of communication at the time of switching the network.
The technique disclosed in JP-A-2008-236079 can perform the communication of the same data simultaneously between a communication terminal provided with a Media Independent Handover (MIH) function and two different network systems. The communication terminal starts the connection with the first network, and monitors radio communication quality between the communication terminal and the first network. The communication terminal, when a monitor result is lower than a preset threshold value of radio communication quality, performs the connection with the second network. The communication terminal starts communication between the communication terminal and the second network using data equal to data used between the communication terminal and the first network. The communication terminal monitors a radio communication quality state between the communication terminal and the second network in the same manner. The communication terminal, when it is confirmed that the communication can be performed with radio communication quality between the communication terminal and the second network exceeding a certain threshold value, disconnects the connection with the first network so that the handover is executed.
In JP-A-2009-049875, a communication terminal performs communication simultaneously with two different networks or with either one of these networks which is communicable. The communication terminal connects with the first network and acquires information such as communication quality between the communication terminal and the first network, power consumption when the communication is performed between the communication terminal and the first network, a communication speed between the communication terminal and the first network, and communication application to be used. In the same manner, the communication terminal can also acquire the similar information between the communication terminal and the second network. The communication terminal uses these monitor values as parameters of handover, and selects the network on a side where power saving can be realized within a range where communication application to be used can be used without troubles. That is, the communication terminal executes a new connection or the handover with the side where power saving can be realized.
<Task to be Solved in Suppressing the Increasing of Cost and in Enabling Early Start of Providing Services in Mounting Functions Under Control of Network>
A conventional handover system between different networks requires dedicated facility for realizing a handover which maintains the continuity of communication not only on a communication terminal but also on respective network sides.
The communication terminal requires a dedicated circuit and software for controlling switching networks. On the other hand, the networks require the provision of a dedicated facility in respective network systems. Accordingly, the initial facility investment necessary for a telecommunication provider is increased leading to a high cost.
Further, to realize the handover which maintains the continuity of communication, with respect to a dedicated facility which is added to a network, it is necessary to take into account easiness of future system migration, roaming or the like. For this ends, generally used is a dedicated facility which supports a method fixed by the standards organization, to be more specific, 3GPP and 3GPP2 in the case of 3G network or LTE, and IEEE and WiMAX forum in case of WiMAX. However, it takes time for review before these standards organizations fix the handover specification between WiMAX or LTE and the existing network. Accordingly, the telecommunication provider faces an obstacle in a handover service between the WiMAX or LTE and a 3G network from the beginning of providing services using WiMAX or LTE in a single form.
With respect to WiMAX and LTE, at the time of starting providing services, a service area is narrow. Accordingly, in general, adopted is a method where the propagation of the service is promoted by maintaining the continuity of communication with the existing network. However, there arises a drawback that the maintenance of the continuity of communication cannot be acquired in an early stage.
<Task to be Solved for Realizing Maintenance of Continuity of Communication>
In performing switching of the system between 3G network and WiMAX/LTE during communication under control of a mobile unit, on a network system where there is totally no exchange between both networks, an IP address before switching of the system and an IP address after switching of the system differ from each other. Accordingly, a change of an IP address is detected by an OS of a posterior terminal (communication terminal to which the mobile unit is connected) such as a PC resulting in the disconnection of active session of communication application.
Even when an interwork is provided between both networks so that the communication is performed on a network system where an IP address is not changed before and after system switching, it is impossible to register two same IP addresses on a PC at system switching timing from a viewpoint of an IP network system. Accordingly, there is timing where IP address is not present before and after system switching. When the communication application performs the exchange of data at this timing, an active session of the communication application is disconnected in the same manner as the above-mentioned task.
<Technique Disclosed in Prior Art Document>
JP-A-2008-236079 discloses the invention relating to a handover method which uses an MIH technique. Usually, to realize the maintenance of the continuity of communication at the time of switching the system in the network system which uses the MIH through an MIH technique, an agent server of the MIH is arranged on a network side. In general, the management of a session including IP addresses of different network systems is controlled on a network side using the agent server of the MIH.
JP-A-2008-236079 completely fails to disclose a method where an IP address is relayed under control of a terminal side. JP-A-2008-236079 also does not refer to as an MIH server. However, it is at least considered that JP-A-2008-236079 discloses a technique which depends on a network side function with respect to the maintenance of continuity of communication at the time of switching the system between the 3G network and the WiMAX/LTE.
JP-A-2008-236079 also discloses an example where a hand-set-type mobile unit is used. In this case, a collective control can be performed on a mobile unit side including the management of an IP session and the management of communication application. Even when an IP address is changed or timing at which IP address is not present at system switching timing, the control of communication application by concealing such a state can be performed relatively easily because of a closed platform. On the other hand, in a case such as a mobile data card where the continuity of communication at the time of switching the system is maintained using a function provided on a platform under an environment of an independent open platform such as a PC, it is necessary to conceal a change of an IP address or the presence of timing at which there is no IP address in the OS or the communication application. However, in JP-A-2008-236079, there is no description corresponding to these techniques.
In JP-A-2009-049875, when the connection terminal is connected to the different kinds of networks, power consumptions, throughputs and the like of the respective networks are measured, and the switching to the different kinds of system is performed by taking into account the characteristic of application to be used and also the power consumption. However, in the same manner as JP-A-2008-236079, in JP-A-2009-049875, there is no description on the constitution which maintains the continuity of communication at the time of switching the system under control of the terminal.